Text Diff Checker
Compare two blocks of text and see exactly which lines were added, removed or left untouched. It uses a longest-common-subsequence comparison — the same approach version control uses — so it identifies the lines that genuinely changed rather than falling out of step after the first difference.
How to compare two texts
- Paste the original text in the first box.
- Paste the changed version in the second box.
- Tap Compare — removed lines show in red, added lines in green.
When you'd use this
- Comparing drafts — Finding what actually changed between two versions of a document.
- Reviewing code — Checking the difference between two snippets without setting up a repository.
- Config files — Spotting the single line that differs between a working and a broken configuration.
- Proofreading — Confirming that an edit changed only what it was meant to.
Good to know
- Comparison is line by line — Whole lines are matched, so a single altered word appears as one line removed and one added.
- Longest common subsequence — The algorithm finds the largest set of lines the two texts share, which keeps everything aligned even when whole blocks have been inserted or deleted.
- Very large texts are refused, not stalled — The work grows with the two line counts multiplied together. Past four million line pairs the tool asks for smaller sections rather than freezing the page.
- Nothing is uploaded — Both texts stay in your browser, which matters when what you are comparing is a contract or unreleased code.
Frequently asked questions
How does the comparison work?
It uses the classic longest-common-subsequence algorithm — the same approach tools like Git use for diffs — applied line by line, entirely in your browser.
Does it compare word by word?
No, line by line. If a single word changes inside a line, that whole line shows as removed and re-added. For prose, putting each sentence on its own line gives more readable results.
Is there a size limit?
Very large texts (millions of line combinations) are declined with a clear message instead of freezing your browser — split them into sections and compare those.
Does it show which words changed within a line?
No, it works at line level. A line with one altered word shows as a removal plus an addition, which is also how most version control tools present a change by default.
Why does it refuse to compare very long texts?
The comparison grows with the two line counts multiplied together, so a large pair would lock the page up for minutes. The limit is four million line pairs, and an honest message asking for smaller sections beats a frozen browser.
Is my text uploaded in order to compare it?
No. Both sides are compared in your browser and never transmitted — which is rather the point when the thing being compared is a contract or source code that has not shipped.